1. Field of the Invention
This invention relates to moderators and stabilizers of footwear, and more particularly to an improved spring moderator and stabilizer which absorbs, redistributes, and stores energy of localized loads and forces, through elastic deformation, and then returns the energy to the user in useful form as the load is removed, while providing comfort and support.
2. Description of the Prior Art
There are numerous articles of footwear in the prior art in which inserts and supporting members are present, principally for the purpose of providing comfortable support to the human foot. For example, U.S. Pat. No. 3,120,712 of 1964 issued to Menken describes a shoe construction which includes a bladder filled to a pressure of about 300 psi. A steel plate overlies the bladder to confine it, and, at a pressure of 30 psi, the plate must support a force of 600 pounds and must, accordingly, be extremely rigid and inflexible.
U.S. Pat. No. 2,237,190 of 1941 issued to McLeod describes a shoe incorporating supporting members of springy material which supporting members are corrugated transversely and are thus rigid in a transverse orientation.
U.S. Pat. No. 3,253,355 of 1966 also issued to Menken also describes the use of a stiff plate over an inflatable bladder.
Other patents exist which describe a stiffening or reinforcing plate in the shoe structure, such as arch support devices and the like.
U.S. Pat. No. 4,183,156 discloses a "moderator" described as uniformly distributing relatively high loads associated with fluid-containing chambers in the shoe structure. The moderator is described as being relatively thin, 0.005 to 0.080 of an inch, and is described as being "semi-flexible" to conform to the dynamic contours of the plantar. This prior moderator, however, does not perform the function of an energy transfer mechanism, but is used solely for foot comfort.
While the above described inserts and supporting members and moderators, as well as others described in the prior art, are said to perform in a manner satisfactory for the purposes therein disclosed, none of the prior art has provided a moderator of the structure and function of the moderator of this invention.
More specifically, the moderator of this invention provides a variety of unique qualities and functions not heretofore achieved. For example, it is known in the prior art to use foamed inserts or inflatable inserts, normally used as in-soles in footwear. U.S. Pat. No. 4,183,156 and U.S. Pat. No. 4,219,945 describe inflatable inserts and combinations thereof with elastomeric materials. The latter patents represent an improvement of the prior art in that the described in-soles absorb localized forces and redistribute these forces from the localized area, the absorption of forces operating throughout the fluid system of the in-sole. In effect, the fluid system acts as a pneumatic spring. The moderator of this invention, which is in the nature of a mechanical spring, enhances and improves the energy absorption, redistribution, storage and energy return of the above types of in-soles. Where the in-sole is an all-foam, non-inflatable type of insert, the moderator of the present invention provides similar improved benefits.
In general, the moderators of the prior are rigid and inflexible and do not conform to the wearer's foot or are rigid and inflexible in order to support the foot in a predetermined manner. Alternatively, some are moldably flexible to conform to a desired contour of the foot. In some of the prior art structures the energy of the applied localized load is merely absorbed, and little, if any, of the absorbed energy is returned in a useful form. Where the energy is merely absorbed, it is usually dissipated in the form of heat and over a period of time the generated heat may adversely affect the footwear.
With footwear to be used in sports related activities, or in severe types of physical activities, the interaction between the foot, footwear and the surface may vary widely, depending upon the nature of the particular activity, the footwear, and the surface. For example, in long distance running, the sequence generally involves heel strike, pronation, and toe-off propulsion phases followed by a "float phase". The foot is actually on the ground only a relatively short period, for example, less than 0.04 of a second, and the loading on the foot may be quite high. In the heel strike phase, from two to eight times the body weight comes down on the heel in a comparatively short period, and the localized loads may range from about 400 to 1,000 pounds. Where the surface is hard, for example, concrete or hardtop, and the footwear is non-compressible, the high loads are absorbed by the heel and transmitted through the related bone structure to the remainder of the body. Thus, from the standpoint of comfort, either a soft running surface or a soft cushioned shoe structure, or a combination thereof would seem to be desirable.
However, the toe-off propulsion phase tends to require firmness because of the propulsion mechanism. Here, a hard surface and a non-compressible shoe structure, or a combination thereof, would seem to be desirable. For footwear of a given type, the effect may be different for different types of surfaces, e.g., sand, concrete, or hardwood surfaces. Sand is yielding and while it cushions heel strike better than does concrete or hardwood, the yielding nature makes toe-off propulsion more strenuous. Concrete and hardwood favor the dynamics of toe-off propulsion, and hardwood is preferable over concrete because hardwood is more resilient than concrete, and tends, to some extent, to cushion heel strike. While the resiliency of hardwood compared to concrete might not seem significant in terms of absolute numbers, it is significant from the standpoint of foot comfort and physical activities.
From the nature of long-distance running, there is a significant impact at heel strike which is returned to the athlete through the calcaneus, and to the legs and torso as an upward and forward energy, i.e., a movement which includes both a vertical and horizontal component. The absorption, redistribution, storage and return of this energy would be of value to a runner. Even small increases in efficiency, as determined by oxygen measurement uptake, are physiologically significant, and can be translated into increased speed. For example, an energy savings of 0.8% is equivalent to roughly one minute and 25 seconds in a three-hour marathon, and about one minute in a two-hour-and-ten-minute marathon. Accordingly, a relatively lightweight, comfortable shoe, which increases efficiency, even if by a comparatively small percentage of two percent to 6 percent, for example, represents a significant advance in the art.
Even the nature of the physical activity is a factor in footwear design and engineering. Long-distance running involves repeating cycles of heel strike, pronation, toe-off propulsion followed by a float phase with reasonably repeatable loads. In basketball, for example, the situation is quite different, because the cycle is not repeatable due to the variety of activities in the sport and the loads encountered when the foot or some portion thereof comes into contact with the floor, and such loads may be significantly higher than those involved in running. A basketball player may come down on the ball or heel of one foot after a high jump and the localized loads encountered may be significantly in excess of those normally encountered in the heel strike phase of long-distance running. Further, the nature of the sport is such that quick starts, stops and changes of direction are all possible in a random, non-cyclicle manner. To some extent, the same is true in sports such as soccer played on artificial turf or grass, but the surface tends to be more resilient than the hardwood surface. Also, tennis presents the same variety of foot motion, although high jumps are not as frequent.
It is known from U.S. Pat. No. 4,183,156 that partilar types of inflatable in-sole structures there described are capable of absorbing localized forces and storing and returning mechanical energy to the foot and leg so as to reduce the "energy of locomotion" consumed in running, walking and jumping. As described in the above-identified patent, displacement energy is absorbed from the foot by the inflated in-sole as the foot makes contact with the ground, the energy being converted to fluid pressure energy and stored within the inflated in-sole and then is converted back to energy of motion at the end of the stride as the foot leaves the ground. The described in-soles are initially filled with a "supergas", which through diffusion later includes those gases contained in air in an amount equal to their partial pressure in air.
While the above-described in-soles operate satisfactorily and include moderators to provide comfort, for some applications it was believed necessary to use relatively high pressures and/or relatively high density foams to withstand the relatively high localized loads produced in certain types of activities such as jumping. Further, while those in-soles were effective in absorbing and converting the energy ultimately into energy of locomotion, more effective use of the available energy was not achieved. More specifically, the redistribution of energy was related to the communicating fluid passages for the air-gas mixture, thus requiring in-sole geometries which tended to be difficult as a practical matter. Elastic deformation was not used as a vehicle in the energy storage or distribution chain and the storage of energy was not as efficient as could be achieved. Even relatively small increases in energy return effect a significant improvement over the prior art structures.
One of the advantages of the inflatable in-sole structures was the adiabatic compression in response to applied loads and the transfer of energy at a relatively high rate approximating the speed of sound, i.e., 1088 feet/second. Energy was also transferred through the elastomeric or plastic material which formed the fluid passages, but the rate of energy transfer was significantly less than that through the air-gas mixture. In the case of foam materials, the rate of energy transfer is relatively slow, e.g., about 100 feet per second or less. The result was that in some instances the dynamics of energy adsorption, distribution and return was not "tuned" to the wearer's activity. The result was that the available energy was not efficiently used, having in mind that even seemingly small increases in energy savings may have a significant impact on the performance of the athlete or the wearer.
It is also apparent that comfort is a factor in athlete efficiency of performance in the sense that the body may expend energy compensating for impact and shock loads experienced in running. The reduction of the effect of these loads by the provision of a comfortable shoe which provides proper support and return of some of the energy involved in shock loads offers advantages not heretofore obtained. In effect, the provision of a shoe which provides comfort and support which does more than merely adsorb and dissipate the shock loads would provide advantages not achievable by the prior art devices.
In view of the foregoing, one of the objects of this invention is to provide an improved moderator which cooperates with the other components of the foowear to absorb, redistribute, store and return energy to the user in a far better fashion than can be achieved by the same structure without the moderator of this invention.
More specific objects of this invention include:
(a) Achievement of a "banked track" effect between the foot and the running surface proportional to the applied vector forces; PA1 (b) Achievement of improved running efficiency when properly combined with an air-gas in-sole system; PA1 (c) Improvement of stability at heel strike and toe-off of footwear regardless of whether and air-gas in-sole system is used; PA1 (d) Providing improved and increased support for individuals defined as "pronators"; PA1 (e) Cooperating with the heel counter of the footwear to create a dynamic cupping action to snug the heel counter more firmly around the heel of the foot at moments of severe downward and lateral impact between the foot and the ground; PA1 (f) Permitting the use of softer foam and/or lower pressure air-gas in-soles to tune more precisely the dynamics of the shoe to the athlete and to the activity, for example, running, tennis, basketball, track, soccer, football, etc.; PA1 (g) Adsorbing, redistributing and storing the energy of localized loads and forces through elastic deformation and then returning the energy to the athlete as the load is removed; PA1 (h) When used with footwear or in-sole constructions of the type described in U.S. Pat. Nos. 4,183,156; 4,219,156; 4,219,945, and 4,271,606 the moderator structure of the present construction PA1 (i) increases the energy adsorption capability of the entire structure; PA1 (ii) achieves a better balance between comfort and firmness in the shoe structure; PA1 (iii) improves the "jump height" blocking and stopping characteristics of tennis and court shoes; and PA1 (iv) enhances and improves the energy absorption, redistribution, storage and energy return characteristics of those shoes and in-sole structures; PA1 (i) Offers the advantage of use of foam in-sole components which are softer, less dense, and thus of lighter weight, while retaining softness in the shoe and providing firmness, while also providing the energy characteristics previously described; PA1 (j) Permits the use of low-pressure and inflatable inserts and lower density foams, while eliminating "bottoming-out", while still providing a soft cushion feel, firmness, support and comfort; and, PA1 (k) Enhances and improves the energy absorption, redistribution, storage and energy return characteristics of the foam or air-gas filled in-sole.